There are many immunotherapy trials being conducted throughout the world ranging from vaccines to T cell transfer and antibody studies. In these trials, aside from the obvious need to assess clinical responses, Investigators must analyze changes in immune responsiveness which results from the immune intervention. Thus, there is a need to collect PBMC from patients at regular intervals both before and following the therapy. These PBMC are cryopreserved to save the PBMC phenotype and function until a later time point when the PBMC can be thawed and assessed to determine if the immunotherapy was effective. In addition, preparation of subsequent doses benefits from a source of readily obtainable PBMC which will respond to in vitro manipulation similar to the day the product was received by the lab. There are few standardized techniques available for cell cryopreservation as it relates to immunotherapy. Most labs have their own protocols which themselves often provide inconsistencies in cell viability and function upon thawing. It is also difficult to evaluate results of immunotherapy trials and make comparisons from lab to lab. The current proposal will focus on cryopreservation medium and compare static vs. controlled rate freezing techniques. In 4 Specific aims, we will examine: 1) optimum medium for cryopreservation. Human serum + DMSO will be compared to Plasmalyte-A, an FDA approved commercial serum free electroyte or rehydration fluid. The comparison of Plasmalyte A to serum is important because if it works, significant cost reduction will occur since the cost per liter is less than 1% of the cost of serum. In addition, this is an FDA approved product which is consistent from batch to batch. The second specific aim will evaluate different methods of thaw. Specific Aim 3 will compare static freeze techniques to controlled rate freezing. The fourth specific aim will monitor Specific aims 1 and 3 by comparing PBMC subset function at various time intervals using assays of cellular immunity. The goal of the proposal will be to develop a strategy for peripheral blood mononuclear cell (PBMC) cryopreservation which can be more universally applied. A more standardized approach will allow a more accurate assessment of immne responsivenss which can be compared between studies in different centers. In addition, other clinical studies utilizing PBMC can also benefit from such a study (studies of HIV and transplantation for instance). The 4 specific aims will be done over a two year period of time.